package com.liu.single;

import com.liu.AbstractList;

/**
 * @author liucong
 * @date 2021/2/15 - 16:46
 *
 * 增加一个虚拟头结点
 */
public class SingleLinkedList2<E> extends AbstractList<E> {
    private Node<E> first;

    public SingleLinkedList2(){
        first=new Node<>(null,null);
    }

    private static class Node<E>{
        E element;
        Node<E> next;

        public Node(E element, Node<E> next) {
            this.element = element;
            this.next = next;
        }
    }

    @Override
    public void clear() {
        first=null;
        size=0;
    }

    @Override
    public E get(int index) {
        return node(index).element;
    }

    @Override
    public E set(int index, E element) {
        Node<E> node=node(index);
        E old=node.element;
        node.element=element;
        return old;
    }

    @Override
    public void add(int index, E element) {
        rangeCheckForAdd(index);

        Node<E> prev = index==0 ? first : node(index-1);
        prev.next=new Node<>(element,prev.next);

        size++;
    }

    @Override
    public E remove(int index) {
        rangeCheck(index);

        Node<E> prev= index==0 ? first : node(index-1);
        Node<E> node=prev.next;
        prev.next=node.next;

        size--;
        return node.element;
    }

    @Override
    public int indexOf(E element) {
        if(element==null){
            Node<E> node=first;
            for (int i = 0; i < size; i++) {
                if(node.element==null)
                    return i;
                node=node.next;
            }
        }else{
            Node<E> node=first;
            for (int i = 0; i < size; i++) {
                if(element.equals(node.element))
                    return i;
                node=node.next;
            }
        }
        return ELEMENT_NOT_FOUND;
    }

    /**
     * 获取index位置对应的节点对象
     * @param index
     * @return
     */
    private Node<E> node(int index){
        rangeCheck(index);

        Node<E> node=first.next;
        for(int i=0;i<index;i++){
            node=node.next;
        }
        return node;
    }

    @Override
    public String toString() {
        StringBuilder string = new StringBuilder();
        string.append("size=").append(size).append(", ").append("[");
        Node<E> node = first.next;
        for (int i = 0; i < size; i++) {
            if(i!=0)
                string.append(", ");
            string.append(node.element);
            node=node.next;
        }
        string.append("]");
        return string.toString();
    }
}
